The present invention relates to poly(alkenyl-co-maleimide) polymers and to the use of such polymers as cocurable compositions with diene rubbers, producing high damping additives for use in rubber compositions.
Imidization between a maleic anhydride and a primary amine group is a known chemical reaction. The synthesis of monofunctional N-alkyl and N-aryl maleimides is also known. They have been used to improve the heat stability of homo- and copolymers prepared from vinyl monomers. Typically, the bulk resins include ABS -poly(acrylonitrile-co-butadiene-co-styrene); SANxe2x80x94a polyblend of poly(acrylonitrile-co-butadiene) and poly(styrene-co-acrylonitrile); poly(vinyl chloride), poly(styrene-co-acrylonitrile); poly(methyl methacrylate); or the like. The maleimides can be copolymerized with other monomers such as acrylonitrile, butadiene, styrene, methyl methacrylate, vinyl chloride, vinyl acetate and many other comonomers. An alternative practice is to produce copolymers of maleimides with other monomers such as styrene and optionally acrylonitrile, and to blend these with ABS and SAN resins. In any event, the polymer compositions are adjusted so that the copolymers are fully compatible with the bulk resins (e.g., ABS and/or SAN) as shown by the presence of a single glass transition point (Tg) as determined by DSC.
Two or more polymers may be blended together to form a wide variety of random or structured morphologies to obtain products that potentially offer desirable combinations of characteristics. However, obtaining many potential combinations through simple blending may be difficult or even impossible in practice. Frequently, the two polymers are thermodynamically immiscible, which precludes generating a truly homogeneous product. This immiscibility is not always a problem since it can be desirable to have a two-phase structure. However, the situation at the interface between these two phases often leads to problems. The typical case is one of high interfacial tension and poor adhesion between the two phases. This interfacial tension contributes, along with high viscosities, to the inherent difficulty of imparting the desired degree of dispersion to random mixtures and to their subsequent lack of stability, giving rise to gross separation or stratification during processing or use. Poor adhesion leads, in part, to weak and brittle mechanical behavior often observed in dispersed blends and may render some highly structured morphologies impossible.
Provision of an extended grafted copolymer having the impact strength of polypropylene, the elastomeric properties of a block copolymer, high damping properties, and thermostability remains highly desirable.
The present invention is generally directed to a process for forming a diene-rubber grafted centipede polymer. The process includes copolymerizing a copolymer comprising a maleimide and at least one monomer unit chosen from the group consisting of vinyl aromatic hydrocarbons, R1R2ethylenes, or alkyl vinyl ethers with an amine. The amine is further functionalized with at least one functional group capable of grafting to a diene rubber. The copolymer is cocured with a diene rubber to form the diene-rubber grafted centipede polymer.
In one aspect of the present invention, a second amine, which is saturated, is reacted with the copolymer comprising a maleimide and at least one monomer unit chosen from the group consisting of vinyl aromatic hydrocarbons, R1R2ethylenes, or alkyl vinyl ethers. The copolymer is then reacted with the first amine.
In another aspect of the present invention, a co-curable rubber composition comprising a diene rubber/and a copolymer is provided. The copolymer includes at least one maleimide unit formed from the reaction of maleic ahydride with an unsaturated amine, and at least one monomer unit chosen from the group consisting of vinyl aromatic hydrocarbons, alkyl vinyl ethers, and R1R2ethylenes. The alkyl vinyl ethers are chosen such that the alkyl group is substituted or unsubstituted, linear or branched, having between 1 and 20 carbons. The R1R2ethylene monomers are chosen such that the R1 and R2 substituents independently are hydrogen, or are substituted or unsubstituted C1 to C20 alkyl groups.
The following definitions apply herein throughout unless a contrary intention is expressly indicated:
The terms xe2x80x9cvinyl aromaticxe2x80x9d and xe2x80x9calkenyl benzenexe2x80x9d are used interchangeably.
The term xe2x80x9cmaleic anhydridexe2x80x9d encompasses dicarboxylic acids, including maleic anhydride, which can form a copolymer with an alkenyl benzene, an alkyl vinyl ether, or an R1R2ethylene, the copolymer having monomer units reacted through the dicarboxylic acid which are capable of reaction with an amine functional group.
The term xe2x80x9cmaleimidexe2x80x9d encompasses the reaction product of an amine and a maleic anhydride, described above.
The term xe2x80x9cR1R2ethylenexe2x80x9d as used herein encompasses monomer units of the general formula: 
where R1 and R2 are the same or different substituents on the same or different carbon atoms of the ehtylene group, and are selected from hydrogen and substituted C1-C20 alkyl groups.